Boot upper



FIG. 1 is a perspective view of a boot upper according to my new design;

FIG. 2 is a right side view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a rear view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a top view thereof.

The broken lines showing the boot sole is for illustrative purposes only, and forms no part of the claimed design. 

The ornamental design for a boot upper, as shown and described. 